In an electric power grid that uses conventional generation technology (e.g., oil-fired, gas-fired, nuclear, hydro) production of electric power is varied to match consumption. Some power plants are base-loaded (i.e., are set to produce constant output) and others have their output controlled to satisfy changing load requirements. There are multiple time horizons over which the power plant production is controlled to balance production against the load on the grid. The shortest time horizon ranging between a few seconds to a few minutes, is focused on maintaining system frequency, and is called regulation. A longer time horizon ranging between a few minutes to a few hours, is focused on balancing supply and demand, and is called load following.
One of the issues with renewable power grid integration is the variability of power production. Conventional methods of addressing this issue include (1) changing the production of conventional, grid-connected power plants in real-time to compensate for the changes in renewable power production, and (2) curtailing the renewable power production below its potential maximum to maintain a pre-scheduled value that can be expected to be maintained based on forecasts. The first approach requires increased use of conventional production and increased variation of that production to compensate for the variability of renewable power production. The second approach foregoes potential renewable power production to provide a lower guaranteed level of output
Some approaches that control loads to assist the grid in load following have been forms of curtailment, including: a) interruptible loads, in which a load such as a manufacturing plant disconnects from the grid and runs on its own power during periods when the grid is stressed, or b) demand management, that includes a variety of strategies in which grid customers are economically induced, generally during periods of peak load on the grid, to either (i) allow specified loads be inhibited by centralized control from operating for specified durations, or (ii) to generally avoid use of appliances or other high power consumption items during those peak periods.